<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <li>这是li标签1</li>
    <li>这是li标签2</li>
    <li>这是li标签3</li>
    <li>这是li标签4</li>

    <script>
    
        var li = document.querySelectorAll('li');
        for(var i = 0; i < li.length; i++){
            li[i].addEventListener('click',function () {
                alert(this.innerText);
            })
            
        }

    
    </script>
</body>
</html>